Glass impregnated carbon articles



Patented Sept-27, 1949 hasta unrrso srares Partnr ortica Augustin L. J.Queneau, Morristown, N. J.

Application July 16, 1947, Serial No. 761,290

This invention relates-to articles or products of carbon or graphiteadapted for a variety of uses, particularly Where strength andresistance to heat, oxidation or the eiiects of corrosive liquids aredesirable.

Carbon, and especially artificial graphite, may be machined readily intoarticles of various shapes and sizes. The material s,however, inherently weak. vIt has been the practice heretofore to impregnate thecarbon or graphite with suitable fusible plastics such asfurfuralresins,

-phenolics and similar materials in order to increase the strength ofthe material. Products made from such compositions cannot be used attemperatures much over 175 C. owing tothe softening or decomposition ofthe plastic constituent. 4

l S tile ObseC; U Auhr! pl'eb'eixi; inviarli/linx tu aiord machinedarticles or products including i Fig. l is a vertical section through anappa-k i ratus suitable for producing articles or products of theinvention; and

Fig. 2 is a sectional view on the line 2 2 of Fig. l.

The desired object is accomplished by impregnating or lling the pores ofthe articles or products of carbon or graphite which may, for example,be preformedv by machining or other- 8 Claims (Cl. 117-421) wise, with asuitable glass. There are a variety of glasses having relatively lowmelting points, i. e. '70D-800 C., and low viscosities which willreadily penetrate the voids in carbon or graphite, particularly underthe inuence of pressure. Upon cooling, the articles or products willhave a non-porous layer of greater or lesser depth, depending upon thetreatment, which will afford additional strength and at the same timeincrease resistance to heat and to corrosion.

Any suitable glass may be employed. For ordinary purposes, I prefer theternary eutectic which isliquid at '150 C. The fluidity of the glass maybe increased by adding small amounts of barium oxide and iron oxides, orby any other treatment well known to those skilled in the art ofmanufacturing glass.

The impregnation of the carbon or artificial ygraphite with glass mayextend throughout the and deposited and hardened in the pores in. situ,f lwith resulting improvement in the character of the article orproduct.

Such articles and products are especially use- I ful in machine parts,for example in pumps for strong acids and other corrosive fluidsincluding molten metal such as zinc. They may be used also 1n the rormor electrones, Iurnace linings and tor other purposes wherever strengthand resistance to corrosion are essential. The invention is not limitedto articles or products of any particular coniiguration or for anyspecific uses, since, as is obvious, carbon or articial graphite can bemachined into a great variety of forms and when impregnated with glass,as hereinafter described, the articles or products may be utilized forany purpose to which they may be adapted.

In producing the articles or products of the invention, any suitableapparatus may be used. One form of such an apparatus is illustrated inthe accompanying drawings, in which 5 indicates a shell of steel orother suitable material having a cover`6 of like material adapted to besecured thereto in gas-tight relation by means of a gasket l. Arefractory lining 8 of any suitable material is disposed within theshell 5 and a similar refractory lining 9 is provided in the cover 6.The apparatus is adapted to be heated in any suitable manner, preferablyby the provision of resistors I0 consisting of metal coils, carbon,graphitesilicon carbide, etc., suitably disposed and connected byconductors il and l2 to any suitable source of electric current. Thus,the temperature of the apparatus may be raised to and maintained at thedesired point.

Within the container consisting of the shell 5 and the cover S, a,receptacle i3 of any suitable refractory material such as mullite,graphite, etc., is arranged to receive the articles or products to betreated. For the purpose of illustration only, I have shown a pluralityof electrodes iii and pump impellers i5 arranged in layers. It will beunderstood that any article or Vproduct to be treated in accordance withthe invention may be similarly disposed fory treatment. Bars i6 ofsuitable refractory materialare disposed above to close the opening 24in the bottom of the receptacle 18.

A pipe 25 extends through the wall of the container and is adapted to beconnected to a suitable vacuum pump (not shown) adapted to exhaust theatmosphere of the container 5. The pipe may be closed by a valve 26. Asimilar pipe 21,controlled by a valve 23, is adapted to be connected toa source of fluid under pressure (not shown), for example, an inert gassuch as nitrogen.

The procedure for the impregnation of articles or products will bereadily understood in view of the foregoing description of theapparatus. The articles or products are disposed in the receptacle I3and are held in place by the bars I6. The cover f 6 is then applied andcurrent is supplied to the resistors l0 until the temperature is at thedesired point, which should be such as to maintain fiuidity of themolten glass. A supply of molten glass is then introduced by removingthe plug I9. After replacement of the plug, the vacuum pump is employedto evacuate the atmosphere to the desired point.

vacuum isdesirable but not critical. It is desirable to remove as muchas possible of the at-v mosphere within the receptacle so that air inthe pere: of the articles te be treated is cffecti"ely eliminated. .Thenthe vacuum is established. the hand wheel 22 is operated to withdraw thevalve 23, permitting the molten glass to flow into the receptacle i3 andsurround the articles or products disposed therein. The articles I4 andl5 have a tendency to float in the molten glass but are held submergedbythe bars I6 and blocks I'l, the latter engaging the bottom of thereceptacle i8.

Thereupon, fluid under pressure, such as nitrogen, is introduced throughthe pipe 21 until the desiredA pressiue is attained. The molten glasssurrounding the articles or products to be treated is forced into thepores of the carbon or graphite. Depending upon the time allowed, theglass will impregnate the carbon or graphite articles to the extent of amarginal layer or throughout the entire thickness thereof. Usually it issufficient to afford impregnation only in a marginal layer. The pressureapplied by the uid such as vnitrogen may be 200 pounds per square inchor over. It is usually sumcient to maintain drawn, the surplus glass maybe separated therefrom and the articles or products allowed to cool atthe desired rate, preferably in a non-oxidizing atmosphere. The surfacesof the articles or products may be cleaned and dressed and are thenready for use.

A relatively high claim 1 in which said surface of the body has ancarbon or artificial graphite of a selected porosity which may @intense@10.150 microns and f in special cases of over 50 microns." The glasslling the pores of the carbon orgraphite to a greater or lesser depth,depending upon the ternperature and pressure at which impregnation iseffected, will increase the tensile strength of the carbon or artificialgraphite to 3000 pounds per square inch or over. Mechanical parts,electrodes and the like of carbon or artificial graphite treated inaccordance with the invention will have at least a marginal layerimpregnated with glass which resists oxidation and the effect ofcorrosive liquids.

Various changes may be made in the procedure as described, as well as inthe apparatus employed, Without departing from the invention orsacrificing the advantages thereof.

1. `An article of manufacture comprising a body machined to its finalform vand consisting of porous carbon having a continuous carbonstructue,substantially all ofthe pores of said body being of afszeexceeding ten microns, and

'the pores immediately adjacent a surface thereof and inwardly therefromfor a substantial depth being filled with glass of relativelylow meltingpoint extending into them from said surface, said glass having beendeposited and hardened in situ. 2;-An article of manufacture as setforth inv claim 1 in which the glass filling the pores has a meltingpoint between about '700 C. and 800 C. 3. An article of manufacture asSet forth in claim l in which the carbon is graphite.

4. An article of manufacture asset forth in eigernaL nonporouslayer ofglass deposited and the body.

5. An article of manufacture comprising a bodymachined to its final formand consistingl of porous carbon having a continuous carbon structure,substantially all of the pores of said body situ.

In manufacturing articles or products in acl cordance with theforegoing, I prefer to employ Number 6. An article of manufacture as setforth in claim 5 in which the glass has a melting point of between about700 C. and 800o C.

"7. An article ci manufacture as set foitlrin.

claim 5 in which the carbon is graphite.

8. An article of manufacture as set forth in claim 5 in which thesurfaces of the body have an external, non-porous layer of glassdeposited and hardened in situ with the glass filling the pores of thebody. AUGUSTIN L. J. QUENEAU.

REFERENCES 'orricnl The following references are of record in th file ofthis patent:

narran STATES PA'I'ENTs Name f Date 1,764,311 Hunt June 17, 19301,868,206 Hunter et al July 19, 1932 2,013,625 Buck Sept. 3, 19352,280,962 McDougal Apr. 28, 1942 i 2,336,565 Parmenter Dec. 14, 19532,394,041 Conradty Feb. 5, 1946

